Interphase Tech ispan 5535 pri Manual Do Utilizador

If the distance is longer (up to 6200 feet or 1800 meters), you 
need to connect the adapter in a DS1 configuration. In this 
configuration, a Channel Service Unit (CSU) must translate 
the short haul DSX1 interface in order to support the longer 
distance.

The iSPAN-PRI adapter optionally supports an internal CSU. 
In this case, you can connect the adapter directly to the T1/PRI 
line, also in a DS1 configuration. If your adapter does not 
include this option (and if the distance is too long), you will 
need to connect the adapter to an external CSU, which itself 
will be connected to the metallic T1/PR1 interface.

You can connect the iSPAN-PRI directly to the line without 
any internal or external CSU if the distance to your carrier is 
short enough (less than 655 feet or 200 meters). The line will 
be in a DSX1 configuration (short haul). See Figure 3-1.

Direct connection is subject to constraints imposed by FCC 
rules and by your partner carrier. For more information about 
these constraints, and to find out if you can connect directly to 
the interface, contact your carrier.